<template>
    <div class='progress-bar' ref="progressBar" @click="progressClick">
        <div class="bar-inner">
            <div class="progress" ref="progress"></div>
            <div class="progress-btn-wrapper" ref="progressBtn" @touchstart.prevent="progressTouchStart" @touchmove.prevent="progressTouchMove" @touchend="progressTouchEnd">
                <div class="progress-btn"></div>
            </div>
        </div>
    </div>
</template>

<script>
import { prefixStyle } from '../../common/js/dom';

const progressBtnWidth = 16
const transform = prefixStyle('transform')
export default {
    props: {
        percent: {
            type: Number,
            default: 0
        }
    },
    created() {
        this.touch = {}
    },
    components: {},
    data() {
        return {

        };
    },
    computed: {},
    methods: {
        progressTouchStart(e) {
            this.touch.initiated = true
            this.touch.startX = e.touches[0].pageX
            this.touch.left = this.$refs.progress.clientWidth
        },
        progressTouchMove(e) {
            if(!this.touch.initiated) {
                return
            }
            const deltaX =e.touches[0].pageX - this.touch.startX
            const offsetWidth = Math.min(this.$refs.progressBar.clientWidth - progressBtnWidth, Math.max(0, this.touch.left + deltaX))
            this._offset(offsetWidth)
        },
        progressTouchEnd() {
            this.touch.initiated = false
            this._triggerPercent()
        },
        progressClick(e) {
            const rect = this.$refs.progressBar.getBoundingClientRect()
            const offsetWidth = e.pageX - rect.left
            this._offset(offsetWidth)
            this._triggerPercent()
        },
        _triggerPercent() {
            const barWidth = this.$refs.progressBar.clientWidth - progressBtnWidth
            const percent = this.$refs.progress.clientWidth / barWidth
            this.$emit('percentChange', percent)
        },
        _offset(offsetWidth) {
            this.$refs.progress.style.width = `${offsetWidth}px`
            this.$refs.progressBtn.style[transform] = `translate3d(${offsetWidth}px, 0,0)`
        }
    },
    watch: {
        percent(newPercent) {
            if(newPercent >= 0 && !this.touch.initiated) {
                const barWidth = this.$refs.progressBar.clientWidth - progressBtnWidth
                const offsetWidth = newPercent * barWidth
                this._offset(offsetWidth)
            }   
        }
    }
}
</script>
<style lang='scss' scoped>
@import "../../common/scss/variable.scss";
.progress-bar {
    height: 30px;
    .bar-inner {
        position: relative;
        top: 13px;
        height: 4px;
        background: rgba(0, 0, 0, 0.3);
        .progress {
            position: absolute;
            height: 100%;
            background: $color-theme;
        }
        .progress-btn-wrapper {
            position: absolute;
            left: -8px;
            top: -13px;
            width: 30px;
            height: 30px;
            .progress-btn {
                position: relative;
                top: 7px;
                left: 7px;
                box-sizing: border-box;
                width: 16px;
                height: 16px;
                border: 3px solid $color-text;
                border-radius: 50%;
                background: $color-theme;
            }
        }
    }
}
</style>